body {
    background: url(../images/竹林1.jpg) no-repeat;
    background-size: cover;
}

#road {
    border-bottom: 7px dashed black;
}

#runner {
    position: absolute;
    background: url(../images/panda_colour.png);
    bottom: 0;
    width: 250px;
    height: 330px;
    animation:walk 1s steps(12) infinite,
               forward 5s forwards;
}

@keyframes walk{
    0%{
        background-position: 0px;
    }
    100%{
        background-position: -3000px 0;
    }
}
@keyframes forward{
    0% {
        left: 0;
    }
    100% {
        left: 50%;
        /* margin-left: -100px; */
        transform: translateX(-50%);
    }
}